Control of a dc power supply

A control circuit for a DC voltage power supply, the control circuit including,

• an operational amplifier having a first input coupled to a negative voltage rail of the power supply, a second input coupled to a ground reference and an output,
• an offset current generator operative to generate an offset current at an output reference node representative of the voltage differential between the negative voltage rail and the ground reference based on the output of the operational amplifier,
• an error amplifier having a first input coupled to the output reference node, a second input coupled to a positive voltage rail of the power supply, and an error amplifier output;
• and
• a modulator coupled to the error amplifier output operative to maintain the positive voltage rail at a select value.

A DC power supply with a control apparatus, the power supply comprising:

• a negative voltage rail to supply ground reference to a device;
• a positive voltage rail to supply a positive voltage to the device;
• a control circuit configured to control the voltage level on the positive voltage rail, the control circuit including,
• an operational amplifier having a first input coupled to the negative voltage rail, a second input coupled to a ground reference and an output,
• an offset current generator operative to generate an offset current at an output reference node representative of the voltage differential between the negative voltage rail and the ground reference based on the output of the operational amplifier,
• an error amplifier having a first input coupled to the output reference node, a second input coupled to the positive voltage rail, and an error amplifier output;
• and
• a modulator coupled to the error amplifier output operative to maintain the positive voltage rail at a select value.

A control circuit for a DC voltage supply, the control circuit comprising:

• a circuit operable to measure a voltage difference between a negative voltage rail and a ground reference in the DC voltage supply, the circuit further operative to create an offset voltage proportional with the measured voltage difference, the circuit further yet operative to add the offset voltage to a reference voltage to create a modified reference voltage;
• an error amplifier having a first input coupled to receive the modified reference voltage and a second input coupled to a positive voltage rail in the DC voltage supply, the error amplifier further having a output;
• and
• a modulator coupled to the output of the error amplifier, the modulator operative to maintain the positive rail at a select value corresponding to the modified reference voltage.